Process for solubilizing iron in the soil utilizing 1-nitroso naphthalene sulfonates



United States Patent 2,996,37'1 PROCESS FOR SOLUBILIZING IRON IN THE SOIL UTILIZING l-NTFROSO NAPHTHALENE SULFONATES Eli Seifter and Norman Phillips, Dayton, Ohio, assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Aug. 19, 1957, Ser. No. 679,079

8 Claims. (Cl. 71-27) This invention relates to a process for solubilizing iron salts which are present in soils but which are otherwise unavailable to growing crops. The invention relates particularly to a process for the utilization of soil-bound iron salts as trace elements in plant nutrition by the treatment of the soil with certain l-nitroso naphthalene sulfonates.

An object of the invention is to provide soil treating compositions for the more efficient utilization of soilbound iron salts in order to render the iron content available as a trace element in plant nutrition. A further object of the invention is to provide compositions which are of utility in the treatment of soil in the fertilization thereof, while at the same time causing the soil-bound iron salts to become available by solubiliz-ing such insoluble salts with a component of the fertilizer mixture.

A still further object is to improve soils by rendering the soil content thereof available to growing crops by reacting the same with l-nitroso naphthalene sulfonates. The said compound may be applied directly to the soil; for example, in aqueous solution or dispersion which may be employed as a direct spray, or the said compound may be introduced in a fertilizer or other soil modifying composition such as a high molecular weight acrylic polymer applied to the soil in order to modify its properties. It has been found that the group of l-nitroso naphthalene sulfonates in which the naphthlene group may be substituted by amino, carb-oxyl, hydroxy, nitroso, nitro, azo and additional sulfonate radicals are of utility in this relationship. The said sulfonate compounds may be utilized as various salts, for example, as the sodium, potassium or ammonium salts.

The relative proportions in which the above-described l-nitroso naphthalene sulfonate compounds are employed in order to solubilize soil-bound iron are from 2.5 to 50 pounds per acre in the crop row. These proportions of the said compounds may be employed by the direct application of such compounds, for example, an aqueous solution or dispersion. In the preparation of a dispersion, it is desirable to make use of typical detergent compounds such as alkyl aryl sulfonate salts as dispersing agents. It has been found that such solutions and dispersions are highly elfective for this purpose and that such solutions release or solubilize up to four times as much iron as do typical commercial chelating compounds, for example, the di or tetra sodium salt of ethylene diamine tetra acetic acid. It has also been found that the present compounds are of greater utility than the prior art chelating compounds for the reason that the solubilized iron can now be provided as ferrous iron instead of the ferric compound, despite the fact that the normal iron compounds exist in the ferric condition in the soil as the result of oxidation by atmospheric oxygen and oxidizing agents which are present in the soil.

The solubilization of the soil-bound iron salts may also be carried out by providing the l-nitroso naphthalene sulfonates as a component of a fertilizer, for example, a typical commercial fertilizer which contains a nitrogen source such as ammonium sulfate together with a potash source such as potassium chloride and a phosphorus source such as ammonium phosphate. In order to supply the above proportions of from 2.5 to 50 pounds per acre of the l-nitroso naphthalene sulfonates per acre of soil, it is desirable that a commercial fertilizer contain from 0.1 percent to 1 percent by weight of the said compound.

In certain soils which are deficient in iron, but in which it would be futile to apply iron 'because'of precipitation thereof in the soil, the present method of treatment may be modified by adding a soluble iron salt together with the above-described l-nitroso naphthalene sulfonates. The iron salt employed for this purpose may be any soluble iron salts such as ferric chloride, ferrous sulfate, ferric nitrate, etc. The proportion of'the iron salt employed together with the above-described solubilizing agent is from 25 to 500 pounds of the iron salt per acre based upon the addition in the crop row, i.e., the addition is calculated only upon the direct area of application, disregarding, the unused free space between the actual rows of growing crops, for example, corn, or fruit trees such as oranges. It is pointed out, however, that the addition of iron is not essential in all soils, but is to be employed only where a deficiency" of iron exists. The characteristics of iron deficiency are well known, for example, in the chlorosis or yellowing of leaves of vegetable or fruit crop grown in such iron deficient soils. It is obvious that soils which contain insoluble iron but require only that the iron be made available can be treated directly with the l-nitroso naphthalene sulfonates without the necessity for adding iron salts.

The following examples illustrate specific embodiments of the present invention.

Example 1 Test plots of an alkaline clay salt and an acid sandy soil containing insoluble soil-bound iron were treated with various proportions of l-nitrosoZ-naphthol-disulfonic acid as an iron solnbilizing agent. Comparison tests were also conducted in which the disodium salt of diethylene diamine tetra acetic acid was utilized in the same relationship. Certain tests also made use of added iron as various salts in order to show the solubilizing effect achieved by the present treating agents. The tests were conducted by applying an aqueous solution or dispersion of the treating agent by spraying the same upon the soil. Samples of the soil were then subjected to leaching with distilled water after which the iron content of the aqueous extracts was determined by conventional analytical methods. It was noted that the soluble iron thus released from the soil and made available as a trace element in soil nutrition existed to a considerable degree as the ferrous salt, even when the iron was provided as an additive material in the ferric condition, or was present in the soil as insoluble ferric salts. The following table summarizes the results obtained:

The above method of testing was also employed making use of an acrd'sandy soil. The results obtained are set forth below:

- Amount Iron salts Treatment Added Extracted i KIM/acre)? (IbJam-e) vit-nitroso-2-naphthohdisulfonicacid; 200 70 disodlum salt of ethylene di e tetr acetic ma I 200 24 'disodium salt of ethylened amtne tetraacetic .-m---- .50 s 'plus FeCh 25 disodium saltofet-hylene diamine tetraacetic acid; ...:....V 200 2. i

plus commercial ohelating additive for Western'acid soils 200 The-above data indicated that the use of the present iron 'solubilizing oomponentsrenders the soil-hound iron available for trace nutrition of plants because the insoluble forms of iron'present in the soil are rendered soluble.

The above-described l nitmsci-Znaphthol-disulfonic "acid was also applied to in which various seeds had been planted. It was found inthis pie-emergence test that the --growth'-of the-seedlings was not hindered by the presence of these iron solubilizing compounds. The preemer genee tests wereconducted with radish, cucumber, oatsandfrye grass seeds an d the solutions of the said soil iuodifying-agents applied by spraying prior to the sproutingof the seeds. The rates of application employed in "thesetests were one hotmdred pounds per acre and fifty pounds per acre, without indicating any herbicidal ef- 'fec't's.

What I'claiin is:

1. Process 'for the treatment of soil containing insoluble iron compounds which comprises treating the said soil with a virtuoso naphthalene sulfonate.

2. Process for the treatment of soil containing insoluble iron compounds which comprises treating the said soil with a rl-nitroso naphthalene sulfonate in combination with aware: soluble iron compound.

3. Process for the treatment of soil containing insoluble iron compounds which comprises treating the said soil with 1-nitrosoZ-naphthol-disulfonic acid.

4. Process for the treatmeht of soil containing insoluble 5 iron compounds which comprises treating the said soil with l-nitroso-Z-naphthol-disulfonic acid together with a water soluble iron salt. r 7

5. Process for the treatment of soil'containing insoluble iron compounds which comprises treating the said soil with l-nitroso-Z-naphthol-disulfonic acid in the proportion of from 2.5 to pounds per acre.

6. Process for the treatment of soil containing insoluble iron compounds which comprises treating the said soil with l-nitroso-2-naphthol-disulfonic acid together with from 25 to 500 pounds per acre of a water soluble iron salt.

7. A soil treating composition comprising as an essential component thereof a fertilizer together with a 1- nitroso naphthalene sulfonate.

8. A soil treating composition comprising as an essential component thereof a fertilizer containing nitrogen, potash and phosphorus together with a 1-nitroso-2- naphthol-disulfonic acid.

References Cited inthe file of this patent UNITED STATESPATENTS 2,284,002 Lontz 1 May 26, 1942 2,786,746 Goldhaar Mar. 26, 1957 2,799,973 Smith July 23, 1957 2,802,728 Jaquier Aug. 13, 1957 2,828,182 Cheroniset a1 Mar. 25, 1958 OTHER REFERENCES Martell, Arthur E., et a1.: Chemistry of the Chelating Agent Compounds, second printing 1953;copyright, 1952, by Prentice-Hall, Inc., N.Y., pages 119 and 503.

Martell, A. E., et a1.: Chemistry of the Metal 'Chelate Compounds, third printing 1956; copyright, 1952, by

0 Prentice-Hall, Inc., N.Y., page 503. 

1. PROCESS FOR THE TREATMENT OF SOIL CONTAINING INSOLUBLE IRON COMPOUNDS WHICH COMPRISES TREATING THE SAID SOIL WITH A 1-NITROSO NAPHTHALENE SULFONATE.
 7. A SOIL TREATING COMPOSITION COMPRISING AS AN ESSENTIAL COMPONENT THEREOF A FERTILIZER TOGETHER WITH A 1NITROSO NAPHTHALENE SULFONATE. 